Circulatory assist devices

The introduction of newer and better elastomers for use in the rubber diaphragm of circulatory assist devices is currently hampered by a lack of shortterm fatigue tests to evaluate candidate materials. 

As an integral member of THI s animal research team, Brano designed and preformed studies involving myocardial protection during cardiac operations, as well as temporary and permanent mechanical circulatory assist devices, heart valve prostheses, and synthetic vascular grafts. In addition he authored, and co- authored approximately 300 publications, and oversaw the writing of numerous heart failure and transplant protocols. 

Severe shock < 90 > 20 < 2.0 Vasoactive drugs, inotropic drugs, circulatory assist devices... 

Oxygenator for Circulatory Assist Devices, Artif. Heart Prog. Con/. Proc.y p. 450-416 (June 9-13, 1969). 

Advances in numerous areas have allowed marked increases in survival times of artificial heart device (AHD) and left ventricular assist device (LVAD) experiments. Successful clinical trials employing LVAD s for temporary post-operative assistance after coronary surgical procedures have been reported by several centers (1). As clinical use of circulatory assist devices progresses, longer term (i.e., 3-4 months) implantations will be needed requiring not only initial surface hemocompatibility, but also long-term surface inertness or stability. 

For several years, Goodyear supplied their compounded polymer under the name of Hexsyn to various research centers namely, Monsanto Research Corporation ( ), Washington University ( 5), National Bureau of Standards ( 6), Cleveland Clinic (2.) and Thermoelectron Corporation ( 8), These institutions have research programs for physical testing of polymers for use in circulatory assist devices and for the development and evaluation of a cardiac prosthesis funded by the NHLB-NIH. 

Kardos, J. L., Sanson, W. H. and Clark, R. E., "Physical Testing of Polymers for Use In Circulatory Assist Devices", Devices and Technology Branch Contractors Meeting Program,... 

Rosenberg, G., 1995, Artificial heart and circulatory assist devices, in The Biomedical Engineering Handbook, J. Bronzino, ed., CRC Press, Boca Raton, FL, pp. 1839-1846. 

Selection of biomaterials for circulatory assist devices is a task made difficult by the complexity of the interfacial interactions between blood and the solid surfaces of candidate materials. Among the major factors contributing to the complexity are surface charge, surface energy, surface roughness, chemical reactivity, adsorptivity, hydrophobicity, etc. To further aggravate the complexity, the factors noted interact with each other in ways that are not as yet understood or well-defined. 

Heparin, a natural protein, is an important constituent of blood and contributes to blood clotting. When circulatory assist devices were first proposed, it was found that the artificial surfaces promoted unnatural thrombosis. An important proposed solution to the problem involved grafting heparin to the surfaces of the materials involved, including such polymers as poly(vinyl chloride) and poly(dimethyl siloxane) (Artificial Heart Program, 1968 Lyman, 1966 Sears, 1965). 

Circulatory assist device, ventricular assist device (VAD), intra-aortic balloon pump — eventual transplantation... 

It is a device able to evaluate the valve performance in conditions similar both to the physiological ones and to the most common cardiovascular pathologies. Such an apparatus has already been described in detail in a previous paper. Besides testing prosthetic valves, this mock circulatory system can evaluate vascular prosthe-ses, left heart replacement pumps, intraaortic balloon pumps and other circulatory assistance devices. Neither the anatomic complexity nor the physiological behaviour can be exactly reproduced, but the simplicity of use and the good results obtained with this device, show its efficiency. 

Reid JS, Rosenberg G, Pierce WS. Transmission of water through a biocompatible polyurethane application to circulatory assist devices. J Biomed Mater Res November 1985 19(9) 1181-202. 

Artificial Heart and Circulatory Assist Devices Gerson Rosenberg. Introduction History of LVADs Engineering Design of Blood Pumps Conclusions References... 

The remainder of this chapter will focus on the application of this engineering design method to the design of artificial hearts and circulatory assist devices. 

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